Abstract
Background:
Antioxidants are important factors in reducing stress on poultry birds. Recently, nanomaterials have been introduced as part of feed additives to enhance the health of birds.

Aim:
This study aimed to evaluate the effects of dietary Nano-Se supplementation on broiler chicken growth performance, serum antioxidant status, and hepatic expression of oxidative stress-related genes. In total, 250 one-day-old Ross 308 broiler chicks were reared for up to 42 days.

Methods:
Birds were randomly assigned to five treatments (n = 50 birds/treatment; 5 replicates of 10 birds each) in a completely randomized design as follows: 1st treatment (T1; basal diet, control), 2nd treatment (T2; basal diet + 0.3 mg/kg organic Se), 3rd treatment (T3; basal diet + 0.3 mg/kg Nano-Se), 4th treatment (T4; basal diet + 0.6 mg/kg Nano-Se), and 5th treatment (T5; basal diet + 0.9 mg/kg Nano-Se).

Results:
Growth performance was recorded weekly. On day 42 , blood samples were collected for biochemical analysis of antioxidant enzymes, including GPx, SOD, TAC, and MDA. Liver tissue was harvested for quantitative real-time PCR analysis of GPX1, SOD1, CAT, Nrf2, and HO-1 gene expression. T4 showed a significant improvement in the final weight and feed conversion ratio. A significant increase in serum GPx activity was observed for T4 compared to T1 at 59.6% (125.3 vs. 78.5 U/mL;P<0.001), respectively. SOD activity and TAC were both increased by 49.1% (42.5 vs. 28.5 U/mL;P<0.001), and was 46.2% (2.85 vs. 1.95 mM Trolox equivalents, P<0.001) in T4 compared with T1. Likewise, MDA concentration was decreased in T4 by 44.4% compared with that in T1 (3.25 vs. 5.85 nmol/mL, P<0.001), respectively. Additionally, hepatic gene expression analysis revealed a significant upregulation of Nrf2 (3.80-fold), HO-1 (4.20-fold), GPX1 (3.45-fold), SOD1 (3.15-fold), and CAT (2.95- fold) in T4 (P<0.001). In conclusion, dietary supplementation with 0.6 mg/kg of nanoSe effectively enhanced the Nrf2-mediated antioxidant efense system, reduced oxidative stress, and enhanced growth performance in broiler chicken.

Conclusion:
These findings support the use of nano-Se as a superior alternative to conventional selenium sources in the diet and could improve the productive and physiological aspects of broilers.

Key words: Broiler; Growth performance; Nano-selenium; Nrf2 signaling; Oxidative stress.